Current distribution membrane cell

There are three types of blisters, water, salt, and others. Water blisters are formed when there is high water transport across the layers. Salt blisters result finm localized heating of the membrane because of high local current density or nonuniform current distribution. Proper cell design can alleviate this problem (Chapter 5). The other type of blister arises when the acidity of the anolyte is high. When the anolyte pH is below 2, the carboxylate layer protonates to a nonconductive carboxylic acid. This will increase the voltage and the internal vapor pressure, and finally result in the formation of voids in the carboxylate layer. 

With distributed current collection hardware, current distribution during cell operation can be evaluated (Yoshioka et al. 2005). It is found that when the inlet RH is low, the highest current density is observed near the gas outlet, where the humidity is relatively high. Thus, the membrane chemical degradation can be accelerated in the gas inlet region since lower RH usually accelerates degradation. 

To measure the current distribution in a hydrogen PEFC, Brown et al. ° and Cleghorn et al. ° employed the printed circuit board approach using a segmented current collector, anode catalyst, and anode GDL. This approach was further refined by Bender et al. ° to improve ease of use and quality of information measured. Weiser et al. ° developed a technique utilizing a magnetic loop array embedded in the current collector plate and showed that cell compression can drastically affect the local current density. Stumper et al."° demonstrated three methods for the determination of current density distribution of a hydrogen PEFC. First, the partial membrane elec-... 

Figure 35. Comparison between simulated and measured current distributions in a PEFC with 15 jum membrane (EW < 1000) and under anode and cathode conditions of 3/3 bar, 1.2/2 stoichiometry, and 75%/0% relative humidity. The cell temperature is 80...

Species, Temperature, and Current Distribution Mapping in Polymer Electrolyte Membrane Fuel Cells... 

The operating current density must therefore be lower than the limiting current density over the entire membrane surface. This requires careful design of the cell to ensure uniform current distribution throughout the membrane and uniform distribution of the electrolyte concentration throughout the cell. 

Nafion-315 is currently used in the SPE cell for brine electrolysis. The SPE electrolyzer exhibits a 15-20% energy savings when compared to conventional brine electrolyzers, primarily due to the decrease in ohmic and cathode overvoltages. Figure 5 shows the schematic of the SPE electrolyzer along with a typical membrane electrolyzer. The current distribution across the membrane of an SPE electrolyzer is more uniform than that of a typical brine electrolyzer. 

J.T. Keating, Sulfate Deposition and Current Distribution in Membranes for Chlor-Alkali Cells. In F. Hine, W.B. Darlington, R.E. White, and R.D. Vaijian (eds), Electmchemical Engineering in the Chlor-Alkali and Chlorate Industries, PV 88-2, The Electrochemical Society Pennington, NJ (1988), p. 311. 

How uniform is the current distribution across the membrane and between the cells ... 

Improvements have been made to the anode and cathode design and fabrication techniques, as well as to the gasket and manifold materials. These have resulted in a uniform current distribution across the active membrane area and increased internal circulation. In addition, the use of modular bipolar paks with the use of only eight bolts reduces cell renewal time. 

FIGURE 10.3.18. Current distribution in a zero-gap type membrane cell. 

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